为了探究方形竖井基坑挡墙后空间主动土压力分布规律，建立了正交挡墙三维有限元分析模型，研究了不同长高比挡墙平动时墙后主动土压力分布及空间滑裂体形状变化规律，并提出考虑挡墙长高比影响的方形基坑空间主动土压力理论计算模型，给出了深筒形基坑的定义和主动土压力合力及其作用点、挡墙中部截面土压力分布的理论公式.通过理论与数值的对比，发现两者吻合较好.研究表明：当挡墙长高比大于临界长高比时，空间滑裂体由中部的库伦主动土楔和角部的曲面体组成；当挡墙长高比小于临界长高比时，滑裂体无平直段，可定义为深筒形基坑，此时随挡墙长高比减小，主动土压力系数由库伦主动土压力系数逐渐减小,滑裂体倾角逐渐增大.
In order to study the distribution of spatial active earth pressure against retaining walls in square shaft excavations, a 3-dimensional finite element analysis model of orthogonal rigid retaining walls is established, and the distribution of spatial active earth pressure and variation of the spatial slip block against translating retaining walls with different aspect ratios are studied. A theoretical model for determining spatial active earth pressure against translating rigid retaining walls with different aspect ratios is proposed. The definition of deep shaft excavations is given. The theoretical formulae for the resultant earth pressure and its acting point and the active earth pressure in the middle section of the wall are presented. Comparing the theoretical and numerical results, it is found that the two are in good agreement. The studies indicate that the spatial slip block consists of Coulomb’s active soil wedge in the middle of the wall and object with curved surfaces in the corner when the aspect ratio of the retaining walls is larger than the critical aspect ratio. When the aspect ratio of the retaining walls is less than the critical aspect ratio, it can be defined as a deep shaft excavations whose sliding block does not have straight section. As the decrease of aspect ratio, the active earth pressure coefficient decreases gradually from the Coulomb’s solution and the sliding angle increases.
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